Audio preamplifiers are important components in sound recording, reproduction, or audio for live concerts or events. In general, an audio preamplifier takes an electrical signal generated from a microphone, a musical instrument, or another sound source as an input, and further processes and amplifies this input signal to generate a desirable level of amplified electrical signal to other components such as main amplifiers, speakers, or recording equipment
Preamplifiers take an important role in determining amplified and/or reproduced sound characteristics of the sound source, because it is generally the first actively-powered stage for the electrical signal generated from the microphone or another sound source, which are highly vulnerable to undesirable distortions or noise introduced during any amplification stages. For example, an undesirable introduction of distortions or noise at or before the preamplifier stage may be magnified by subsequent amplification stages, thereby making post-preamplifier stage correction difficult and exacerbating any problems from the preamplifier to recording equipment or a listener.
Therefore, a novel first-stage preamplifier design (i.e. interchangeably called herein as a “pre-preamplifier”) that provides a high-fidelity first-stage gain (i.e. a first-stage “lift” in signal from the sound source) to reduce the need of a larger single-stage jump in a subsequent amplification stage may be highly advantageous in minimizing undesirable noise and distortion for multi-stage amplification of audio recording or live performance.
Moreover, a novel preamplifier design that can intelligently and selectively provide signal gain and/or processing to a microphone-originating sound signal source and a musical instrument-originating sound signal source for the first-stage amplification while automatically selecting an appropriate high impedance, low impedance, and/or transformer-coupled signal pathway, depending on the nature of a sound signal source (e.g. microphone-originating, instrument-originating, etc.), may be highly advantageous to a user in an audio recording or live performance environment, because the user can utilize the same novel first-stage preamplifier box to handle various types of sound signal sources without needing to change or swap preamplifier equipment.
Furthermore, in the audio equipment industry, impedance matching or bridging between a sound signal source (e.g. a microphone, a musical instrument, etc.) and a preamplifier has been an important requirement for high fidelity electrical signal transmission between an output from the sound signal source and an input to the preamplifier. Conventional methods of impedance matching or bridging between the sound signal source and the preamplifier include using a commonly-used impedance value at the output of the sound signal source and the input of the preamplifier. A less used but another conventional method of impedance matching or bridging between the sound signal source and the preamplifier is varying the output impedance value of a sound signal source by adjusting the sound signal source's passive circuitry before the output of the sound signal source is transmitted to any active power elements or a preamplifier.
These conventional methods of impedance matching or bridging are typically only used for efficient signal transmission between the sound signal source and the preamplifier, and are not designed to produce customized effects for various sound characteristics at a preamplifier stage. Because the preamplifier is generally the first stage for active circuit processing of a sound source signal, certain customized effects for sound characteristics (e.g. an emphasis on a mid-range audible frequency, an emphasis on treble or bass, or other intended sound effects) may be best obtained at the preamplifier stage without causing significant amount of undesirable noise or distortion to the sound source signal.
Therefore, it may be advantageous to provide a preamplifier unit that can vary impedance loading conditions to obtain customized, desired, and/or adjustable sound characteristics at the preamplifier stage. It may be also beneficial to provide various embodiments of preamplifiers with different impedance loading adjustment interfaces.